Add relative imports so 1.0 and 0.9x can co-exist.

I understand that to use the ES client with a 0.9x ES install, you need to use a different branch than with the 1.x.   However, when migrating an index from 0.9x to 1.x, it would be really helpful to support having both branches available to you using different folder/module names. 

The two libraries can co-exist in different folder names as long as you change certain imports to relative imports. I've made that change here.